1. Field
The present embodiments generally relate to apparatus and methods for urea production.
2. Description of the Related Art
Urea can be synthesized by reacting ammonia and carbon dioxide to form ammonium carbamate, and subsequently dehydrated to form urea and water. The reaction of ammonia and carbon dioxide to form urea can be described using the following equilibrium reactions:2NH3+CO2NH2COONH4 (ammonium carbamate, exothermic)NH2COONH4H2O+NH2CONH2 (urea, endothermic)The first reaction producing ammonium carbamate is an exothermic reaction and essentially goes to completion. The second reaction for producing urea is endothermic and usually does not go to completion. The conversion of ammonium carbamate to urea increases as the temperature and NH3/CO2 ratio increase and decreases as the H2O/CO2 ratio increases. The resulting product can be a urea solution containing one or more contaminants, including ammonium carbamate, ammonia, carbon dioxide, and water, which must be removed to produce a purified urea product.
Conventional methods for removing contaminants in the urea solution have used multiple stages and multiple pieces of equipment. The equipment (i.e. high pressure carbamate condenser, high pressure ejector, medium pressure equipment, pumps, etc . . . ) is expensive to construct, install, maintain, and operate. The equipment must be fabricated out of material that can withstand high temperatures, pressures, and corrosive environments, which is expensive.
There is a need therefore, to reduce the amount of unconverted ammonium carbamate, ammonia, and water in the urea solution. Furthermore, there is a need to reduce the equipment cost required to produce urea.